Severe thunderstorms were moving across portions of southern Wisconsin on Friday evening, the National Weather Service in Sullivan said.

At 5:24 p.m., trained weather spotters in southwestern Fond du Lac reported hail as big as ping-pong balls, according to the weather service.

A severe thunderstorm watch was in effect for most of southern Wisconsin, including the Milwaukee and Madison areas, until 11 p.m. Friday.

A severe thunderstorm watch, outlined in blue, is in effect until 11 p.m. for all of southern Wisconsin.(Photo: Storm Prediction Center)

The storms could bring damaging wind gusts, torrential rain and large hail, the weather service said.

The storms will eventually make their way to the Milwaukee metro area, but whether they remain severe by that time remains a question, said Ben Miller, a meteorologist at the National Weather Service in Milwaukee.

"It'll be pretty late in the evening," before the storms reach Milwaukee, he said.

A number of events, festivals and concerts are on the docket around Wisconsin this weekend, including Bastille Days in downtown Milwaukee.

Other events include Rock USA, Lifest, Wausau Balloon and Rib Fest, the Hodag County Festival and Gathering on the Green.

Anyone attending outdoor events in the next few hours across southern Wisconsin should prepare to take cover should any storms turn severe, the weather service said.